Hello everyone!

I'm working on a black hole that I picked up in non working condition.

Looks to have set for a very long time.

I did all ground mods to all the board's and a new power cord. I removed the battery and corrosion damaged parts from the mpu and cleaned the board and repopulated the components.

The game boots, I can play, sounds and speech are functioning.

I am having a problem with the battery backup. I have this same problem with and without battery connected.

I've got "8" credits all the time and the high score is "888888".

Is this a possible 5101 fault?

Any info would be great!

Thanks! -Matt

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It looks that way but it's not shorting. I'll change that though.

Thanks for the extra eyes.

Any way to test that without a logic probe or scope? You are talking about the 5101 ram yes?

Ok, I don't have an easily available spare but I do have a spare mpu that I could desolder it from!

I'll inspect the board really well to see if I can find any broken traces as well.

Thanks!

I'm working on removing the 5101 from my spare board right now but for !#&$'s and grins, I did the system test "20" and it shows 5101.. Go figure.

Ok, well put the 5101 in to the good board. Still no go. Guess it's a possibility I had 2 bad 5101's..

I verified I'm getting 4v on pin 22. Now what?

On a side note, I can start the game and play. Soon as I game over, it goes right back to 8 credits.

I checked continuity, on the data lines. No breaks. I put a new 5101 in still the same thing.

8 credits, and a high score of "888888" that won't clear. As soon as you drain the last ball in play it automatically goes right back to 8 credits.

Could this be a bad 6502?

On a side note, I'm ordering a logic probe so I can test these TTL and CMOS chips.

Yea, rest of the game works. Just this one problem I can't figure out.

Any idea of what Z4 and Z36 does in the circuit. I see it is outputting to pin 17 and 19 of the 5101.

Chip enable perhaps? Could this cause my problem?

I don't think any settings are getting saved but I'll verify that tonight when I'm at the machine.

I do get a 5101 error while doing a system self test. I'm thinking the chip enable isn't high so the chip isn't even recognized as being in circuit.

I can start a game with no battery attached. I can actually start a 4 player game which will bring the credits display down to "4". Soon as the last ball drains from the 4th player, it will automatically go back to "8" credits.

Nice feature lol.

Well everyone! I fixed the problem! After studying the schematic for awhile and reading over the 5101 specs. Pin 17 is the chip enable for low power mode and pin 19 is the chip enable pin. I decided to swap out z36 (4069) which feeds pin 19 on the 5101. Bingo! I now have no free credits and high score isn't showing "888888".

Thanks for everyone's help!

It is always a good feeling when you finally troubleshoot the electronics yourself!